Saponification of organic esters of cellulose



UNITED STATES PATENT OFFICE SAPONIFICATION OF ORGANIC ESTERS OF CELLULOSE Henry Dreyfus, London, England No Drawing. Application September 5, 1935, Se-

rial No. 39,287. In Great Britain September Claims. (011. 8-20) This invention relates to improvements in the organic ester forming the basis of the artificial manufacture of artificial materials, and particumaterials being saponified, and which are resistlarly to improvements in processes for the saponiant to alkali and can be stripped from the matefication of artificial materials containing cellulose rials after saponification. Examples of such dye- 5 acetate or other organic esters of cellulose. stuffs are 5 The saponification of artificial materials con- Benzoazurme G (Colour Index No. 502) taming cellulose acetate or other organic ester Benzopurpurin 43 (Colour Index N O 448) of cellulose 1s well-known and 1s, 1n general, car- Congo Oran e R (C01 I d N 459) ried out by treating them with media containing g our n ex 10 caustic soda or other suitable basic substance for Dlrect steel Blue BB (Colour Index 465) 10 exam 18 sodium Silicate ammonia or or 'anic Benzo New Blue 5B (Colour Index No. 466) bases The saponification of the materials may Chicago Blue R (Colour Index 474) be carried to a stage in which all the ester groups Bmhant Blue G (Colour Index are removed, or only a partial saponification of the cellulose ester may be effected. The object Dlrctprown M (colwr Index 420) 1 of the present invention is to provide a simple sirlpplng may be Carried-Out ou y ith means of ascertaining visually when the saponilmmedlately after saponification at a y fication has proceeded to the desired extent. Subsequent m y su t l st ppi a nt According to the present invention saponificamay be employed, SOdium ph 20 t is allowed t proceed m colour h Preferably the dye should be one which can be 20 due t t presence of a colouring agent, having discharged effectually without the use of a leucodifferent affinities for the saponified and the unp saponified t has progressed t predeter- The following example illustrates the invenmined degree, and thereafter removing the colour due to the presence of said colouring agent from Example 25 the ester- A cellulose acetate fabric is saponified in a h dyejstufis employed acqordingfio the pres bath comprising a 1-3% aqueous solution of causent mventlon may be dyes WhlCh, while they have tic Soda to which has been added 10% of sodium little or no afiinity for the organic ester forming Sulphate and of benmpurpurin 43 both 80 the basis of the artificial material, have anafilnity calculated on the weight of the fabric for regenerated cellulose, are resistant to alkali From time to time test portions of fabric are the conditions employed in the saponfica' removed and rinsed, dried, and compared with a treatmentrand can SuPSequenflY be stripped series of standards consisting of samples of the r the P Sapomfied materialwh same fabric which have been saponified to various r such dyestuffs are mcorporated in f sawmfiymg predetermined degrees, and subsequently dyed medlum the Progress of the 'f under the same conditions as the fabric which is marked by a gradual colouring of the artificial to be po ified materials, the depth of colour increasing as the s p nifi ti is continued until a sample, degree of sapomficablon mcreasesw the after rinsing and drying, exhibits substantially 40 Shade reaches the depth correspondmg to the the same shade as the standard which has been 0 degree of saponification required, which may be a ifi d to the desired extent detefrmmei? by Commune the mammal bemg In a similar way other suitable cotton dyes, pomfied wlth prevlously prepared standard for instance any of those referred to above, may ponification may be interrupted and the materials be employed fiifiz fi iggfi' most valuable the sapom The principle of the present invention may fication of artificial materials by batch processes, 2:3 2; f iggi g g g gfi gig g g 23E333:

1 for m the form of hanks cops or other before the saponification process with a dyestuif packages. In this method it is necessary only to immerse the materials in the saponifying medium Whlch has no amnity for cellulose and which W111 50 dissolve out from the regenerated cellulose perand maintain them there until they have acquired the desired shade. tion of the materials into the alkali medium. Ex-

As stated above, any suitable dyestuffs may be amples of such dyestuffs are mono-carboxylic employed which have an afiinity for regenerated and mono-sulphonated azo dyestuffs having an cellulose but have little or no aflinity for the aflinity for cellulose acetate or the other organic 55 ester of cellulose concerned. According to this modification of the process the saponification may be carried out until the original shade of the .cellulose ester materials has decreased until it reaches a standard shade.

While the present invention is of particular importance in relation to the saponification of artificial materials containing cellulose acetate, it may also be employed in the saponification of materials containing other organic esters of cellulose, including mixed esters and ether-esters, for example cellulose acetate-propionate, cellulose propionate, cellulose butyrate, ethyl cellulose acetate and oxy-ethyl cellulose acetate.

What I claim and desire to secure by Letters Patent is:

1. Process for the saponification of organic esters of cellulose, comprising treating the ester with a saponifying medium until a color change, due to the presence in the saponifying medium of a coloring agent having different afiinities for the saponified and the unsaponified ester, has progressed to a predetermined degree, thereupon interrupting the saponification, and thereafter removing the color due to the presence of said coloring agent from the ester.

2. Process for the saponification of filaments, threads, ribbons, films and like materials having a basis of an organic ester of cellulose, comprising treating the materials with a saponifying medium containing a coloring agent which has an afiinity for regenerated cellulose but none for the.

cellulose ester until the materials have become colored to a predetermined shade by said coloring agent, thereupon interrupting the saponification, and thereafter removing the color due to said coloring agent from the materials.

3. Process for the saponification of filaments, threads, ribbons, films and like materials having a basis of an organic ester of cellulose, comprising treating the materials with a saponifying medium containing a cotton dye capable of discharge by reduction which has an aflinity for regenerated cellulose but none for the cellulose ester until the materials have become colored to a predetermined shade by said dye, thereupon interrupting the saponification, and thereafter discharging said dye by treating the materials with a reducing agent.

4. Process for the partial saponification of filaments, threads, ribbons, films and like materials having a basis of cellulose acetate, comprising treating the materials with a saponifying medium containing an amount of the saponifying agent greater than that required to efiect saponification to a predetermined degree and a coloring agent which has an aflinity for regenerated cellulose but none for the cellulose acetate, until the materials have become colored to a predetermined shade by said coloring agent, thereupon interrupting the saponification, and thereafter removing the color due to said coloring agent from the materials.

5. Process for the partial saponification of filaments, threads, ribbons, films and like materials having a basis of cellulose acetate, comprising treating the materials with a saponifying medium containing an amount of the saponifying agent greater than that required to effect a predetermined degree ofsaponification, and a cotton dye capable of discharge by reduction, which has an aflinity for regenerated cellulose but none for the cellulose acetate, until the materials have become colored to a predetermined shade by said dye, thereupon interrupting the saponification, and thereafter discharging said dye by treatment with a reducing agent.

HENRY DREYFUS. 

